Heat exchanger



Patented Sept. 25, 1934 HEAT EXOHANGER Alfred Schack, Dusseldorf-Oberkassel, Germany Application September 5, 1931, Serial No. 561,511 In Germany September 10, 1930 1 Claim.

In heat exchangers into which the stream of heating gas enters in a direction transverse to the direction of flow of the heat absorbing medium, as in tubular recuperators, used for the recovery 5 of heat from heating gases, such as waste furnace gases, the first row of a number of parallel rows of tubes against which the heating gas first impinges is subjected to very high temperatures, as it receives the full efiect of the large volume of gas in front of it. The same applies to the crosssection of the inlet in plate recuperators. The danger to the structural elements in front cannot be avoided by introducing into the heat absorbing stream of the endangered rows means for increasing the transmission of heat. These means involve a heavy loss of pressure with a resultant reduced velocity of flow in the tubes. This reduction in velocity of flow on the one hand prevents the attainment of the intended increase in the co-efficient of heat transmission of the cooling medium and on the other hand undesirably raises the temperature of the heat absorbing medium.

No beneficial result is secured by introducing eddy producing bodies and the like in the endangered rows of pipes, but on the other hand the temperature of the tubes is raised.

The present invention is concerned with a method of heating air or gases by means 'of--a heat exchanger and consists in reducing the resistance to flow in the endangered passages (hereinafter referred to as tubes) as compared with that present in-the non-endangered passages or tubes. Where the tubes are provided with internal members which increase heat transmission, the tubes which are subjected to the greatest heat may be protected by making the said members in the endangered tubes shorter or thinner and thereby decreasing the resistance and 40 increasing the velocity of flow through the said endangered tubes. As a uniform pressure prevails in the inlet end of the set of tubes in question, and a different uniform pressure in the outlet therefrom,. each tube of the set of tubes .in question is subjected to a uniform drop in pressure, independent of its cross-sectional area. Consequently there flows through the tubes 9. quantity of heat absorbing medium which is increased where the resistance is less in the endangered tubes in relation to the resistance of the remaining tubes. The effect of the increased volume of heat absorbing medium is to reduce the issuing temperature of such medium without appreciably affecting the co-eflicient of heat transmission. This produces the desired reduction in the temperature of the walls of the tubes. It is frequently advisable to extend this means of reducing resistance in a correspondingly reduced measure to the second or third row of tubes if these are endangered.

The invention is illustrated by way of example in the accompanying diagrammatic drawing.

Figure 1 is a sectional elevation of a form of heat exchanger according to the invention.

Figure 2 a cross-sectional plan view of the heat exchanger shown in Figure l.

In the construction represented in the drawing the tubes a which are subjected to the fiercest heat are of the same diameter as the tubes b which are more distant from the source of heat, and all the tubes are provided with inset bodies which serve to improve the transmission of heat to the gases flowing through the tubes. In order, however, to reduce the resistance in the tubes a, which are subjected to the most severe conditions of heat, the insertions or filling bodies 0 are provided shorter than the bodies 0 in the tubes 1) so that the resistance to flow is reduced.

I claim:

A heat exchanger comprising a set of tubes of uniform diameter throughout, chambers respectively disposed at the ends of the set of tubes and into which the said tubes open and between which the air or gas flows in one direction only, an enclosure for the set of tubes and chambers, which enclosure is provided with oppositely disposed openings for the passage of the heating medium intended to transmit heat to the heat-absorbing medium flowing in the tubes, and filling members extending to a determined distance along the said tubes from the chamber supplying the heat-absorbing medium to the tubes, the said members being of uniform cross-sectional area but of shorter length in'the tubes upon which the heating agent first impinges, the tubes in the set of tubes being all of the same diameter.

ALFRED SCHACK. 

